It is known to reactivate carbonaceous adsorbents in a two-stage fluidizing reactor which comprises a round reactor vessel with two superimposed apertured inlet bottoms. Below the lower inlet bottom there is provided a combustion chamber in which, through combustion of gas or oil, a propelling gas is generated which rises upwards through the apertured bottoms of the fluidizing beds. The gas causes a fluidizing action on the materials disposed on the inlet bottoms while expelling the adsorbed matter. The gas then is discharged from the upper space above the upper fluidizing bed.
Experience has shown that the two fluidizing beds show substantial differences in temperatures in case a wet contaminated activated carbon is charged into the reactor. In the upper fluidizing bed a drying process takes place together with an elimination of the easily desorbed materials at temperatures above about 150.degree. C. The lower fluidizing bed serves more for the reactivation proper which takes place at temperatures above 600.degree. C. and in case of certain contaminations even above 800.degree. C. Thus, a complete regeneration of the carbon is obtained.
Baffle plates are provided on the inlet bottoms or in the fluidizing beds in a direction across to the flow of the material in order to permit the material to flow in a uniform manner and with a constant residence time of each individual activated carbon grain from the upper fluidizing bed to the lower fluidizing bed. For this purpose the discharge of the regenerated activated carbon is also controlled depending on the water contents of the introduced contaminated carbon and the temperature in the area of the discharge space.
After longtime investigations it has been found that interruptions in this process which occur from time to time are caused by the fact that the overflow of the carbon from the upper to the lower fluidizing bed is highly sensitive to the amount of charge in the upper fluidizing bed because of changes in the density of the material or because of clogging up of the apertured bottom of the upper fluidizing bed. The higher the resistance is in the upper fluidizing bed and in its apertured bottom, the more propelling gas will be passed through the overrun tube into the upper fluidizing bed. Since this involves an autocatalytic effect there can occur a complete emptying of the lower fluidizing bed because of excessive spilling of the material into the upper bed which phenomenon results in a complete cessation of the operation.
It was very difficult to recognize this phenomenon since the interior of the reactor is hardly, and the connecting tube is not at all visible during the operation.
It is therefore an object of the invention to avoid these disturbances of continuous operation of the reactor.